This invention relates to means for mounting a protective cab on a tractor, and more particularly, to such means which provide resilient resistance in all directions of movement of the cab relative to the tractor and in addition, provide a varying spring rate of resilient resistance under certain conditions.
Earth-moving and construction vehicles frequently have roll-over protective structures mounted thereon to protect the operator against injury from the overturning of the vehicle. Such protective structure should, of course, provide proper protection for the operator in the event of such overturning. Consequently, the means for mounting the protective structure to the vehicle must be designed with this problem particularly in mind.
A secondary, but still very important problem encountered in mounting such a rollover protective structure to a vehicle is that of isolating the protective structure from shock loads and vibrations set up by normal vehicle operations. This problem is aggravated on a tractor type vehicle since such a vehicle is generally operated on relatively rough terrain, and the protective structure mounted thereon is consequently subjected to shock loads in all directions. Mounting means for mounting the protective structure to the vehicle should ideally be designed with this problem in mind also. Further, such mounting means should be relatively simple in design and allow for the easy removal of the protective structure from the vehicle so that the components therebeneath may be easily reached and serviced.
Although various mounting means can be found in prior patents (see, for example, U.S. Pat. No. 3,203,728 to Wood, U.S. Pat. No. 3,036,858 to Fingerut, and U.S. Pat. No. 3,527,474 to Boersma), it has been found that such mountings have not been totally effective under the conditions as set out above. Initially, it should be pointed out that each of such mountings includes resilient means, i.e., a rubber member, which supports the protective structure with a single, relatively high, spring rate which has been found to be not particularly effective in stopping protective structure panel vibration. Furthermore, it will be seen that none of these patents provides means for resiliently resisting movement of the protective structure in all directions relative to the vehicle body, i.e., shock loads in certain directions will not necessarily compress the rubber member provided.